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United States Patent |
6,057,654
|
Cousy
,   et al.
|
May 2, 2000
|
Method and apparatus for automatically controlling a lighting load
Abstract
In a method of automatically controlling a lighting load to which are
delivered alternately forced turning on instructions and forced turning
off instructions, according to the result of comparing the brightness
measured in a given area and particular brightness thresholds, the
brightness threshold used to deliver a forced turning on instruction,
hereinafter called the comfort threshold, is left for the user to
determine. In a normal operation phase, i.e. after an initiation phase,
the brightness threshold used for delivering a forced turning off
instruction is the sum of this comfort threshold and the brightness
difference between the brightness measured before the previous forced
turning off instruction and the brightness measured immediately after that
forced turning off instruction. Applications include automatic control of
fluorescent tubes with a non-electronic ballast.
Inventors:
|
Cousy; Jean-Pierre (Verneuil Sur Vienne, FR);
Sabourdy; Alain (Limoges, FR)
|
Assignee:
|
Legrand (Limoges, FR);
Legrand SNC (Limoges, FR)
|
Appl. No.:
|
311152 |
Filed:
|
May 13, 1999 |
Foreign Application Priority Data
Current U.S. Class: |
315/308; 315/149; 315/158; 315/294 |
Intern'l Class: |
G05F 001/00 |
Field of Search: |
315/149,134,158,159,307,308,294,297
|
References Cited
U.S. Patent Documents
4347461 | Aug., 1982 | Carlson | 315/158.
|
4431947 | Feb., 1984 | Ferriss et al. | 315/151.
|
4839562 | Jun., 1989 | Francis et al. | 315/149.
|
5821703 | Oct., 1998 | Callahan et al. | 315/317.
|
Foreign Patent Documents |
0563696 | Oct., 1993 | EP.
| |
0744882 | Nov., 1996 | EP.
| |
4428278 | Sep., 1995 | DE.
| |
683478 | Mar., 1994 | CH.
| |
Primary Examiner: Philogene; Haissa
Attorney, Agent or Firm: Young & Thompson
Claims
There is claimed:
1. A method for automatically controlling a lighting load to which are
delivered alternately forced turning on instructions and forced turning
off instructions, according to the result of comparing a brightness
measured in a given area and particular brightness thresholds, wherein the
brightness threshold used to deliver a forced turning on instruction,
hereinafter called a comfort threshold, is left for the user to determine,
and in a normal operation phase, i.e. after an initiation phase, the
brightness threshold used for delivering a forced turning off instruction
is the sum of said comfort threshold and the brightness difference between
the brightness measured before the previous forced turning off instruction
and the brightness measured immediately after that forced turning off
instruction.
2. The method claimed in claim 1 wherein the user is provided with a
parameter-setting unit for setting the required comfort threshold.
3. The method claimed in claim 1 wherein during said initiation phase the
time for turning off said lighting load is chosen arbitrarily.
4. Apparatus for automatically controlling a lighting load including a
brightness detector adapted to deliver information related to brightness,
learning means which receive the information delivered by said brightness
detector and which, in response to a learning instruction, are adapted to
measure and to store in memory the difference between different values of
said information, decision means that receive the information delivered by
said brightness detector and that stored in memory by said learning means
and which, on the basis of said information, are adapted to deliver forced
turning on or forced turning off instructions, and control means which, in
response to said instructions, are adapted to control said lighting load,
wherein for implementing a method as claimed in claim 1 the apparatus
further includes at least one parameter-setting unit available to the user
to enable the user to set a convenient brightness threshold at which a
forced turning on instruction is to be triggered.
5. The control apparatus claimed in claim 4 wherein said decision means are
adapted to deliver to said learning means, before each forced turning off
instruction, a learning instruction such that said learning means take
account of the value of the information delivered by said brightness
sensor before said forced turning off instruction.
6. The control apparatus claimed in claim 5 wherein said learning means are
adapted to take account several times in succession of the value of said
information delivered by said brightness detector after a forced turning
off instruction and to calculate the average of the corresponding values.
7. The control apparatus claimed in claim 4 wherein said brightness
detector includes, in succession, a brightness sensor and a
voltage-frequency converter.
8. The control apparatus claimed in claim 4 including at least one
peripheral unit also controlling said decision means.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns automatic control of artificial lighting to
obtain a satisfactory brightness.
The problem is to slave the lighting load providing the artificial lighting
to the actual brightness in a given area, for example a user's
worksurface.
At present, the lighting load is usually continuously controlled for this
purpose.
The present invention is directed to the situation in which, in contrast,
for diverse reasons including economic ones, the lighting load is
controlled on an on/off basis by delivering to it alternately forced
turning on instructions and forced turning off instructions.
2. Description of the Prior Art
This is the situation, for example, when the lighting load employs
fluorescent lamps, because continuous control of these lamps requires an
electronic ballast, which is particularly costly, and so continuous
control of these lamps is rarely used in practice, in some geographical
areas at least, and depending on installation practice, in particular
because of its cost.
When the lighting load is controlled on an on/off basis, the brightness
measured in the given area concerned is usually compared with particular
brightness thresholds.
In one prior art implementation, for example, a forced turning on
instruction is systematically delivered if the brightness measured is less
than a given percentage of that which the lighting load can provide and a
forced turning off instruction is systematically delivered if the measured
brightness is above a different given percentage, in practice a higher
given percentage, of that brightness, in practice with allowance
systematically being made for the brightness difference between the
brightness values measured before and after a forced turning off
instruction, for example using an average calculated over several turning
off instructions. This is for "training" the system.
In one such prior art implementation the lighting load is therefore
controlled independently of the user.
Also, inevitable aging of the lighting load concerned is not taken into
account.
What is more, an implementation of the above kind cannot take account of
variations in brightness due to failure of a lamp. The brightness produced
by the lamps may then be very different from that which can be assured by
the lighting load and which provides the basis for defining the
percentages used for the forced turning on and off instructions. In this
case, the forced turning on and off instructions may correspond to
brightness thresholds that are uncomfortable for the user.
A general aim of the present invention is to provide a method and apparatus
allowing for the requirements of the user in order to improve user
comfort.
SUMMARY OF THE INVENTION
According to the invention, the brightness threshold taken into account for
delivering a forced turning on instruction, which is chosen to correspond
to the minimum brightness required by the user, and which is referred to
hereinafter for convenience only as the comfort threshold, is left for the
user to determine and in a period of normal operation, i.e. after an
initiation phase, the brightness threshold acted on to deliver a forced
turning off instruction is obtained by adding the comfort threshold and
the brightness difference between a brightness measured before the
previous forced turning off instruction and a brightness measured
immediately after that forced turning off instruction.
Accordingly, the invention provides a good compromise between the comfort
threshold required by the user and optimum and therefore economic control
of the lighting load providing any additional illumination that may be
necessary.
The features and advantages of the invention emerge from the following
description given by way of example and with reference to the accompanying
diagrammatic drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the control apparatus in accordance with the
invention.
FIG. 2 is a diagram illustrating the operation of the apparatus during a
system initiation phase followed by a normal operation phase.
FIG. 3 is a diagram showing the operation of the system over several days
in more detail.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1, the overall aim is to control automatically a lighting
load 10 providing artificial lighting to complement other lighting, for
example natural lighting, or substituted for such lighting.
The lighting load 10 can of course comprise a plurality of separate light
sources which can be controlled independently of each other.
However, for simplicity, it is assumed here that there is only one light
source.
The control apparatus 11 for automatically controlling the lighting load 10
includes, as known per se, a brightness detector 12 adapted to deliver
information related to the brightness L in a given area, for example the
user's worksurface, learning means 13 which receive the information
delivered by the brightness detector 12 and which, in response to a
learning instruction, measure and store in memory the difference between
different values of that information, decision means 14 which receive the
information delivered by the brightness detector 12 and the information
stored in memory by the learning means 13 and which, on the basis of that
information, deliver forced turning on or off instructions, and control
means 15 which are adapted to control the lighting load 10 appropriately
in response to such instructions.
In accordance with the invention, the control apparatus 11 further includes
at least one parameter-setting unit 16A, 16B, 16C, etc. available to the
user so that the user can set an appropriate brightness threshold at which
they require a forced turning on instruction to be triggered. In practice,
this unit is a user interface.
As shown diagrammatically in FIG. 1, for example, a plurality of
parameter-setting units 16A, 16B, 16C, etc. can be provided in parallel.
For example, they can be a data bus, an infrared remote controller and/or
one or more multi-position thumbwheels for setting an extended range of
brightnesses.
The range of brightness can be stepped from 0 to 1000 lux, for example, in
increments of 64 lux, given that for most persons the minimum brightness
threshold below which it is not desirable to reduce background lighting,
referred to hereinafter for convenience only as the comfort threshold S,
is generally around 500 lux.
Of course, the numerical values given above by way of example must not be
considered in any way limiting on the invention.
As shown diagrammatically in FIG. 1, the comfort threshold S set by the
user on one of the available parameter-setting units 16A, 16B, 16C, etc.
is written into a memory 18, where it is stored, and by means of which the
decision means 14 take account of it.
In the embodiment shown, the brightness detector 12 includes, in
succession, a brightness sensor 19, for example a photodiode, which
delivers a voltage related to the background lighting and a
voltage-frequency converter 20 that converts the previous voltage into a
frequency variation.
The corresponding information is supplied simultaneously to the learning
means 13 and to the decision means 14.
In accordance with the invention, the decision means 14 are adapted to
deliver to the learning means 13, before each forced turning off
instruction, and as symbolized by the return connection 22 in FIG. 1, a
learning instruction causing the learning means 13 to take account of the
value of the information delivered by the brightness detector 12 before
the forced turning off instruction.
In accordance with the invention, the learning means 13 are adapted to take
account also, at least once, of the value of the information delivered by
the brightness detector 12 after a forced turning off instruction.
They are preferably adapted to take account several times in succession of
the value of the information delivered by the brightness detector 12 after
a forced turning off instruction and to calculate the average of the
corresponding values.
This average is based on three successive acquisitions of the information
delivered by the brightness detector 12, for example.
On each forced turning off instruction, the learning means 13 measure and
store in memory the difference between the value of the information
delivered by the brightness detector 12 before that forced turning off
instruction and one or more values of that brightness after that
instruction, so updating each time the information that they thereafter
deliver to the decision means 14.
As in the embodiment shown in FIG. 1, the control apparatus 11 preferably
includes at least one peripheral unit 23A, 23B, 23C, etc. controlling the
decision means 14 via formatting means 24 and possibly in accordance with
combinatory applications.
As shown diagrammatically, a plurality of peripheral units 23A, 23B, 23C,
etc. can be provided in parallel, for example an override pushbutton, a
communication bus, a remote controller, an infrared remote controller
and/or a presence detector, such as a motion detector, for determining if
there is anyone in the area concerned.
The foregoing description shows that, in a manner that is known per se, the
control apparatus 11 delivers alternately to the lighting load 10 forced
turning on instructions and forced turning off instructions based on the
results of comparing the brightness L measured in a given area by the
brightness detector 12 and particular brightness thresholds.
It also follows from the foregoing description that, in accordance with the
invention, the user is provided with a parameter-setting unit 16A, 16B,
16C, etc. for setting one of the thresholds, to be more precise the
required comfort threshold S.
In other words, the minimum brightness threshold to be used in delivering a
forced turning on instruction is left to the choice of the user.
In the FIG. 2 diagram time t is plotted on the abscissa axis and the
brightness L measured by the brightness detector 12 is plotted on the
ordinate axis.
It is assumed hereinafter that the brightness L is initially greater than
the comfort threshold S set by the user. The shaded area corresponds to
the brightness contributed by the lighting load when it is turned on.
It is then assumed that, as shown, the brightness L drops until at time t1
it reaches the comfort threshold S. In an initial phase of operation,
called the initiation phase, the user turns on the lighting load 10 using
one of the available peripheral units 23A, 23B, 23C, etc.
It will now be assumed that, during the initiation phase I, the brightness
L measured by the brightness detector 12, at time t2, after stabilization
of the lighting load 10, reaches a value S'1 deemed arbitrarily to be
sufficient to dispense with the artificial lighting provided by the
lighting load 10.
At this time t2 the user then turns off the lighting load 10 using one of
the peripheral units 23A, 23B, 23C, etc. The control apparatus then
measures the difference D between the brightness immediately before and
after the forced turning off at time t2 and stores the value of that
difference.
In other words, in accordance with the invention, during the initiation
phase the time t2 for forced turning off of the lighting load 10 after it
has stabilized is chosen arbitrarily.
This does not apply afterwards, i.e. in a normal operation phase, shown
diagrammatically at II in FIG. 2, and during which the decision means 14
automatically deliver to the lighting load 10 alternating forced turning
on instructions at times like t'1 and forced turning off instructions at
times like t3.
The brightness threshold S'2 considered at time t3 for delivering a forced
turning off instruction is the sum of the comfort threshold S and the
brightness difference D between the brightness measured immediately before
and the brightness measured immediately after the previous forced turning
off instruction.
In this way the brightness L is normally returned automatically and
directly to the comfort threshold S each time L exceeds S by the amount D.
The foregoing operations are repeated as the brightness L changes.
Accordingly, in the normal operation phase II, if the brightness L measured
by the brightness detector 12 falls below the comfort threshold S, the
decision means 14 deliver a forced turning on instruction and if the
brightness L becomes greater than the sum of the comfort threshold S and
the difference D measured at the time of the previous forced turning off
instruction they deliver a forced turning off instruction to the lighting
load 10 and a learning instruction to the learning means 13.
In FIG. 3, as in FIG. 2, time t is plotted on the abscissa axis and the
brightness L measured by the brightness detector 12 is plotted on the
ordinate axis. Again, the shaded area corresponds to the brightness
contributed by the lighting load when it is turned on. The remaining
brightness is deemed to be that due to natural lighting from outside the
area.
In the example of operation of the apparatus shown in FIG. 3, it is assumed
that it is originally night-time, that the lighting load is turned on, and
that the comfort threshold S10 has been programmed.
The user causes the lighting load to be turned off at time t10, for example
by leaving the area. The brightness detector 12 measures the brightness L
in the area just before and just after time t10 at which the lighting load
is turned off. The learning means 13 measure and store in memory the
brightness difference D10 between the measured brightnesses before and
after the load is turned off at time t10.
At time t11, before daybreak, for example on coming into the area at the
start of the day, the user turns on the lighting load 10 using one of the
peripheral units 23A, 23B, 23C, etc.
At time t12, i.e. at daybreak, the brightness due to natural lighting
begins to increase until, at time t13, it exceeds the brightness value
corresponding to the comfort threshold S10.
At time t13 the decision means 14, noting that the brightness L exceeds the
value S10+D10, automatically delivers to the lighting load 10 a forced
turning off instruction. Again, the learning means 13 measure and store in
memory the brightness difference D10 between the brightness measured
before and after the load is turned off at time t13.
After time t13 the brightness in the area, due entirely to natural
lighting, varies above the comfort threshold S10 and then falls until it
reaches the comfort threshold S10 at time t14, whereupon the decision
means 14 automatically deliver a forced turning on instruction to the
lighting load 10.
At time t15, after nightfall, the user leaves the area and turns off the
lighting load manually. Again, the learning means 13 measure and store in
memory the brightness difference D10 between the brightness measured
before and after the load was turned off at time t15.
At time t16, before daybreak, the user turns on the lighting load 10.
At time t17 one of the lamps constituting the lighting load fails and the
brightness in the area drops by an amount D11.
At time t18, i.e. at daybreak, the brightness due to natural lighting
begins to increase until, at time t19, it exceeds the brightness value
corresponding to the comfort threshold S10.
If the brightness due to the lighting load had not changed at t17, the
decision means would have turned off the lighting load at a time t19 at
which the brightness would have exceeded the value S10+D10. At time t19,
the brightness having a value S10+D11 which is less than S10+D10, the
lighting load remains on.
At time t20, after time t19, the decision means 14 note that the brightness
L exceeds the value S10+D10 and automatically deliver a forced turning off
instruction to the lighting load 10. The learning means 13 measure and
store in memory the brightness difference D11 between the brightness
measured before and after turning off at time t20.
After time t20, the brightness in the area, due entirely to natural
lighting, initially varies above the comfort threshold S10 and then falls
until it reaches the comfort threshold S10 at time t21, whereupon the
decision means 14 automatically deliver to the lighting load 10 a forced
turning on instruction.
At time t22, after nightfall, the user leaves the area and turns off the
lighting load manually. Again, the learning means 13 measure and store in
memory the brightness difference D11 between the brightness measured
before and after the load was turned off at time t22.
At time t23, before daybreak, the user turns on the lighting load 10 using
one of the peripheral units 23A, 23B, 23C, etc.
At time t24, after daybreak, the decision means 14 note that the brightness
L exceeds the value S10+D11 and automatically deliver a forced turning off
instruction to the lighting load 10. Again, the learning means 13 measure
and store in memory the brightness difference D11 between the brightness
measured before and after the load was turned off at time t24.
After time t24 the brightness in the area, due entirely to natural
lighting, varies above the comfort threshold S10. During this period, at
time t25, the user replaces the lamp that failed at time t17.
At time t26 the user who replaced the lamp turns on the lighting load to
check if the new lamp works. At time t27, the detector means having
determined that the brightness in the area is greater than the value
S10+D11, the decision means deliver a forced turning off instruction to
the lighting load. At time t27+.DELTA.t the lighting load is turned off.
The learning means 13 measure and store in memory the brightness
difference D12 between the brightness measured before and after the load
was turned off at time t27+.DELTA.t. In the example shown, .DELTA.t is too
brief to be seen in FIG. 3.
In practice, D12 is close to D10 but is not exactly the same because the
new lamp does not contribute exactly the same brightness as the lamp which
failed at time t17. Also, in practice, the brightness due to the other
lamps of the lighting load may have changed between times t17 and t27.
In practice, between the time t26 at which the lighting load is turned on
and the time t27 at which the detector means measure the brightness, there
is a time-delay pre-programmed in the memory 18 which allows the lighting
load to stabilize. The brightness measured at t27 is therefore reliable.
After time t27+.DELTA.t the brightness in the area, which is due entirely
to natural lighting, is stable and thereafter decreases. At time t28 it
reaches the comfort threshold S10. The decision means 14 automatically
deliver to the lighting load 10 a forced turning on instruction.
At time t29, after daybreak, the user leaves the area and turns off the
lighting load. Again, the learning means 13 measure and store in memory
the brightness difference D12 between the brightness measured before and
after the load was turned off at time t29.
In the example of operation shown in FIG. 3, the threshold S10 is constant
for three days. The user can at any time choose a different comfort
threshold using the parameter-setting units 16A, 16B, 16C, etc.
In the example of operation shown in FIG. 3, at time t27 the apparatus
automatically turns off the load and stores the change in the value of the
brightness due to the lighting load. This could be because the user
manually triggers storage in memory of the value D12 by issuing a turning
off instruction instead of the apparatus. In this case the user brings
about an initiation phase, as previously described with reference to FIG.
2.
In the example of operation shown in FIG. 2, to begin the initiation phase,
the user chose a time at which the brightness in the area was equal to S,
but could equally well have chosen a time at which the brightness was
different from S.
Turning off in the initialization phase can be manual, as at t2, or
automatic, as at t27.
The various means employed in the control apparatus 11 in accordance with
the invention and in particular the learning means 13 and the decision
means 14, being sufficiently defined by their functions, their practical
implementation is not described here, the skilled person knowing how to
implement such functions.
Also, the various means can very simply be integrated into a microprocessor
25, as shown in chain-dotted outline in FIG. 1, and merely consist in the
algorithms necessary for the corresponding functions.
Of course, the present invention is not limited to the embodiment described
and shown, but encompasses any variant execution thereof.
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